To find the concentration of NaCl produced in the reaction, we first need to determine the limiting reactant.

Calculate the moles of NaOH:
Moles of NaOH = Volume (L) x Concentration (mol/L)
Moles of NaOH = 0.2 L x 1 mol/L
Moles of NaOH = 0.2 mol

Calculate the moles of HCl:
Moles of HCl = Volume (L) x Concentration (mol/L)
Moles of HCl = 0.05 L x 4 mol/L
Moles of HCl = 0.2 mol

Since the moles of NaOH and HCl are equal, HCl is the limiting reactant.

Using the balanced chemical equation, we know that 1 mole of NaOH reacts with 1 mole of HCl to produce 1 mole of NaCl.

The moles of NaCl produced will be equal to the moles of HCl, which is 0.2 mol.

Calculate the volume of the solution after reaction:
Total volume = Volume of NaOH + Volume of HCl
Total volume = 200 mL + 50 mL
Total volume = 250 mL = 0.25 L

Calculate the concentration of NaCl:
Concentration of NaCl = Moles of NaCl / Total volume
Concentration of NaCl = 0.2 mol / 0.25 L
Concentration of NaCl = 0.8 M

Therefore, the concentration of NaCl produced in the reaction is 0.8 M.